feat(classes): session roster + manual waitlist promotion

Adds the roster and manual promotion controls deferred from the booking
lifecycle milestones. Businesses can now inspect who holds a seat and who
is queueing on a class session, and promote waitlisted customers by hand
— including a deliberate over-capacity override when the session is full.

Backend:
- GET /v1/catalog/class-sessions/{id}/roster — session metadata plus
  confirmed and waitlist entry lists with queue positions
- POST /v1/catalog/bookings/{id}/promote — 409 on a full session unless
  allowOverCapacity is set; 400 for non-waitlisted, 404 for missing or
  foreign bookings; reuses the shared confirm path so waitlist ledger
  rows resolve and reminder jobs re-arm
- ListBookingsBySession repository method (pgx + memory); ClassSession
  carries waitlistCount; UpcomingBooking carries classSessionId and
  waitlistPosition
- OpenAPI paths + schemas, regenerated client, catalog service tests

Frontend:
- classes tab session rows expand into a two-column roster panel with
  per-entry promote buttons and an explicit confirm-anyway step on 409
- booking detail modal shows waitlist position and offers promote for
  waitlisted bookings; list badges show #N queue positions
- CS/EN i18n keys and seeded demo roster data; demo mutations surface
  the demo notice

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/internal/api/server.go

@@ -740,10 +740,28 @@ func NewServer(cfg config.Config, pools *db.Pools) (*Server, error) {
 		}
 		c.JSON(http.StatusOK, gin.H{"status": "cancelled"})
 	})
-
-	// ============================================
-	// CATALOG API - Blocked Days
-	// ============================================
+	protected.POST("/catalog/bookings/:bookingID/promote", func(c *gin.Context) {
+		var request domain.PromoteBookingRequest
+		if err := c.ShouldBindJSON(&request); err != nil && !errors.Is(err, io.EOF) {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid_request"})
+			return
+		}
+		err := catalogService.PromoteBooking(c.Request.Context(), auth.PrincipalFromContext(c), c.Param("bookingID"), request)
+		if err != nil {
+			status := http.StatusInternalServerError
+			switch {
+			case errors.Is(err, catalog.ErrTenantMembership), errors.Is(err, catalog.ErrBookingNotFound):
+				status = http.StatusNotFound
+			case errors.Is(err, bookings.ErrNotWaitlisted):
+				status = http.StatusBadRequest
+			case errors.Is(err, bookings.ErrSessionFull):
+				status = http.StatusConflict
+			}
+			c.JSON(status, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, gin.H{"status": "confirmed"})
+	})
 	protected.GET("/catalog/blocked-days", func(c *gin.Context) {
 		from := time.Now()
 		to := from.AddDate(0, 3, 0) // 3 months ahead
@@ -1063,6 +1081,19 @@ func NewServer(cfg config.Config, pools *db.Pools) (*Server, error) {
 		}
 		c.JSON(http.StatusCreated, response)
 	})
+	protected.GET("/catalog/class-sessions/:sessionID/roster", func(c *gin.Context) {
+		response, err := catalogService.ListSessionRoster(c.Request.Context(), auth.PrincipalFromContext(c), c.Param("sessionID"))
+		if err != nil {
+			status := http.StatusInternalServerError
+			switch {
+			case errors.Is(err, catalog.ErrTenantMembership), errors.Is(err, catalog.ErrClassSessionNotFound):
+				status = http.StatusNotFound
+			}
+			c.JSON(status, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, response)
+	})
 	protected.DELETE("/catalog/class-sessions/:sessionID", func(c *gin.Context) {
 		err := catalogService.DeleteClassSession(c.Request.Context(), auth.PrincipalFromContext(c), c.Param("sessionID"))
 		if err != nil {